VOA常速英语:Researchers Reveal Complete Genetic Sequence of Cow

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An international consortium of researchers has completed mapping the genetic blueprint of the domestic cow, a source of nutrition and livelihood for billions of people around the world. Scientists say the landmark accomplishment will lead to better food production and improvements in human medicine.

The completed bovine genome map is the first full sequencing of a mammalian livestock species. It provides new insight into what makes a cow a cow and identifies important genetic traits that distinguish it from humans and other mammals.

The map, published Friday in the journal Science, is the fruit of a six-year international research effort called the Bovine Genome Sequencing and Analysis Project. The consortium of 300 international scientists mapped the nearly 22,000 genes, or hereditary building blocks, of a Hereford cow - a beef-producing ruminant in wide use around the world.

Scientists compared the cow genome to that of seven other mammals - including the human, dog, rat, mouse, opossum and platypus - and found they share a core set of more than 14,000 genes.

Humans share 80 percent of their genetic sequence with cows, according to the scientists, who say we're more closely related to bovines than to rats and mice.

Researcher Kim Worley at the Baylor College of Medicine in Houston, Texas, which spearheaded the research, says the completed map of the cow genome has implications for laboratory research into new drugs.

"What that means is that when we want to study something that's a human protein we might get better information by studying it in cattle than in mice and rats," Worley said.

Jane Peterson of the Human Genome Project at the US National Institutes of Health, which helped fund the consortium's research, says the cow has been a model for studying human hormone disorders. She says having the entire gene sequence available for study makes the cow a more useful research tool.

"Bovine insulin, for example, was used to find the composition of insulin. And it's also been a model for studying many of the endocrine diseases and the conditions in female cows that are directly related to human[s]," she said.

Cracking the bovine genetic code will also make it a lot simpler and cheaper for cattle breeders to enhance the desirable traits in cattle to produce higher-quality milk and meat, according to geneticist Curt Van Tassell, with the U.S. Department of Agriculture in Beltsville, Maryland.

Van Tassel led a team comparing the bovine sequence in the Hereford cow to six other breeds of cattle, studying important variations, and focusing on the special genes governing cattle reproduction, digestion, lactation and disease resistance.

He says breeders will no longer have to wait years for a bull to produce offspring to learn whether they have desirable genes. 

"Specifically what we're able to do is generate a genetic value for a bull the day he's born essentially ... that replaces a process that took six to seven years and $25,000 to $50,000 by collecting performance data on daughters," he said.

A commentary in Science magazine hails the landmark genetics work, predicting that the bovine genetic roadmap may lead to many other important spin-offs.